32 samsung lcd will not turn on just blinks 5 times

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

i also got 24v on the FAN7530 Pin 8

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

First of all, sorry i didn't really answer your questions and i was only asking things without really checking out. I`m a newbie BTW. I got confused by this website http://www.tongelectronic.com/index.php?topic=2811.0 , which some guy here tried to translate it to me (because i don`t understand this language)

Let me start again,

I got 6 Samsung LA32B350F1 from a school here in laos with all the same problems. Sound but no picture. As i followed that Thai instructions, I removed RP823 which gave me back the screen. It was like it worked normally. But than when i had some power fluctuation (meaning 220v drops to 180v sometimes 160v) for just a split second, the screen just go off. After disconnecting the power cable for 10 sec. it worked again till the next fluctuation. I then used a UPS and it kept working.

Please correct me if i'm wrong, but i think the mainboard and the T-con are still ok and the problem only lies in the Powerboard.

So here are the voltage of the main connector :
1 = 0.75
2 = 5.18
3 = 0
4 = 13.02
5 = 0
6 = 0
7 = 5.18
8 = 5.18
9 = 0
10 = 13.02
11 = 13.02
12 = 5.18
13 = 0.04
14 = 0.04
15 = 0.79

What is the next step i could test ? BTW i tested the 3 diodes near the big cap off board already and no leaking.

DP804 and DP810 : diode mode = 420 / OL. In ohm : no leaking
DP805 : diode mode = 360 ??? but no leaking in ohm.

Big Cap : standby and power on tested only 260v "RP823 back in place"

Thanks for reading this long msg.

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

CN802 tested with RP823 back in place. Also PIN 8 on FAN7530 i measured is 12.26v (sorry for this but that same guy (translator / newbie electrician also) told me it was 24v).

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

It makes sense that whne voltage drops down then the TV stop working, it is because the PFC circuit is not working. If your power line is 220V, then the voltage on the large cap should be 220 x 1.414 = 311VDC when you plug the TV in the outlet, whenyou turn on the TV, the PFC circuit should startup, then the voltage on the cap should go up to about 390~400VDC. If that is not happening, then we need to troubleshoot that sction further. The AC voltage in yiur country is very poor and it is hard on the circuit especially when it drops down to 160VAC, the regulator circuit will try to draw more current to maintain the same DC voltage at all time so it will draw more current through all the switching devices (MOSFET's, transformers, etc.).

"So here are the voltage of the main connector :
1 = 0.75
2 = 5.18
3 = 0
4 = 13.02
5 = 0
6 = 0
7 = 5.18
8 = 5.18
9 = 0
10 = 13.02
11 = 13.02
12 = 5.18
13 = 0.04
14 = 0.04
15 = 0.79 "

What is the connector number? CN802? so I can look at the diagram.
I will look at the diagram further and give you some test points to test.

[vinceroger69]

Re: 32 samsung lcd will not turn on just blinks 5 times

http://translate.google.co.uk/transl...topic%3D2811.0
i still cant make sense of it

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

OK, those voltage on the connector, are they taken when the TV is OFF and when the TV is ON?
CN802 of the power supply board has 16 pins, so I am not sure what connector that is, I need the voltage reading of CN802 of the power supply when TV is OFF and when TV is ON.
The main thing we need to find out right now is the DC voltage on the large filter cap CP815.

[tom66]

Re: 32 samsung lcd will not turn on just blinks 5 times

I have encountered many power supplies which don't work below about 180V, it is quite possible it simply isn't capable of working there.

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

I am not surprised that the TV will stop working with that much brown out, hopefully his UPS has some kind of switched taps regulator to at least maintain the output at 200VAC.
That many brown outs several times a day may mess up the EEPROM.

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

those test were indeed on CN802. IP board bn44_00289b

I forgot this PIN 16 = 0 (GND), These were tested with the cable disconnected from the mainboard.

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

I think the UPS is regulated because i tested it (with rp823 out) and it was still working when the power fluctuated several times.

Not in my case "i think" but maybe something for ricosavy : on this german website problem with another "sound but no picture". Repaired in a shop by changing DP805 "ultra fast rectifying diode, 600V 3A", mentioned in the last post.

Wizard even mentioned this in post #11 in following thread https://www.badcaps.net/forum/showth...LN32B360C5DXZA

maybe to much info

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

So it sounds like your TV will function OK without having the PFC/Voltage boosting working due to at 220VAC input, the power supply will put out around 310VDC which is enough to run the backlight inverter circuits, but if the line drops down to 160VAC, the DC will be only 226VDC which is more likely to be too low for the TV to function correctly.
Since you have already replace the PFC controller IC and it still does not work, then you will have to check the PFC Diodes DP805, MOSFET QP802S, reisistor RP820, inductor LB802, 805, 806.

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

"
DP804 and DP810 : diode mode = 420 / OL. In ohm : no leaking
DP805 : diode mode = 360 ??? but no leaking in ohm.
"
QP802S : tested on board and has Ohm (much higher than 30 ohms) on S-G, S-D, G-D
RP820 : shorted, 0 Ohm (Is this a 12k Ohm?? markings on it says R12K, but on the diagram it says 0.12 Ohm) I redlined this on the picture.
LB802, LB805, LB806 : measured all of them 0 Ohm

I will replace the RP820 as soon as i know the value and also i need to find it somewhere in an old TV. There are no radioshacks around here in this city (luang prabang BTW)

Thanks again Budm, i really appreciate your help.

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

RP820 is OK, I have you tested it because if the MOSFET is shorted, this resistor will burn up, since it is OK, then your MOSFET is not shorted.
Ok, next test points are:
The DC voltage on pin1, and both DC and AC reading of the Gate drive pin 7 of the PFC IC. The voltage on the Drain pin of the QP802S.
There is not much to this section of the PFC at all, we already know that the VCC is OK for the IC.

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

Pin1 = DC 1.85v
Pin7 = both DC and AC 0v

i also discovered that CP804 has shortened (where do i find this cap ? i have a bunch old computer materials here "mainboards, PSU, old crt screens etc ...", and how can i check it is 0.47nF 50v)

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

CP804 is the bypass cap for the MOSFET Source resistor RP820 (0.12 Ohm), that is why the cap shows low resistance reading (the cap is in parallel with 0.12 Ohm resistor). To be sure, lift up one leg of the RP820 and see what you get.
Right now we can see that you are not getting any drive output signal from pin7 of the PFC IC at, something is keeping it off some how. I need to study the IC to see what can cause the lock out at the output.
Lets take the resistance reading between ground pin pin 6 and pin 1, 3, 5, and 7 to see if any one of them has low Ohm reading.

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

CN802 measured on mainboard side connected.

PIN//STBY//PW-ON
1 = 0 // 1.13
2 = 5.19 // 0
3 = 0 // 0
4 = 13.04 // 13
5 = 0 // 0
6 = 0 // 0
7 = 5.19 // 5.15
8 = 0 // 5.15
9 = 0 // 0
10 = 13.04 // 13
11 = 13.04 // 13
12 = 0 // 5.15
13 = 0.04 // 2.19
14 = 0 // 0.16
15 = 0 // 0
16 = 0 // 0

!!! on pin8 and pin12 in STBY connected onboard i got 0 volt, but when disconnected from mainboard i got for pin8=15.18v and pin12=15.18v

I checked this because it was not the same like my first tests in post #42. Back then i tested cable disconnected from mainboard.

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

You should take the reading at the power supply board with STBY, and TV ON and have the main board connected.
You should have on 5VDC at pin 2, 7, and 8 this is an always on power supply which should be there when you plug the TV into the outlet.
Pin 12 is for the backlights inverter on/off, when TV is on, it should have >3VDC on this pin (backlight on).

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

the CP804 is not shorted.

Reading PFC IC with pin6 as gnd.
1= 30.8 kOhm
3= OL
5= 10 kOhm
7= 8.5 kOhm

I will do the reading on CN802 again

[budm]

Re: 32 samsung lcd will not turn on just blinks 5 times

Boy, I do not see why your PFC is not working. One thing about Samsung TV is that if you do not have the CN802 connected to the main board, when you plug the TV into th outlet, the backlights should come on. I do not believe you have problem at CN802.
Pin 7 resistance does not look right, as you can see, that pin is connected to the resistors/diode network and return to ground through 10K resistor (RP806), that means the resistance cannot not be less than 10K! Unless you have Gate to Drain resistance leakage or internal resistance of the IC itself. I would either remove the MOSFET or unsolder the Gate pin, or lift pin 7 of the IC.

[phuong78]

Re: 32 samsung lcd will not turn on just blinks 5 times

Budm, what do you think about the readings for DP805 i posted before #42. This ultra fast rectifying diode i got readings in diode mode of 360 off board.

is this reading too low or normal for this kind of diode ? Check samsung bulletin : http://dc195.4shared.com/doc/C_niqLZi/preview.html

Today (electricity quite stable) readings on big cap = 290V in STB and on PWON it jumps to 400V but immediatly it falls back to 290V. When i plug in the power cable without the mainboard connected, the backlight flashes 1 sec.

What is the next step i can test ? I hope with your help we can fix it today